Non-grounded or metallic circuit system



A. E. KEITH.

NON GROUNDED 0R METALLIC CIRCUIT SYSTEM. APPLICATION FILED APR. 18. 1901. RENEWED MAR. 29.1919.

1,321,313. Patented Nov. 11, 1919.

2 SHEETS-SHEET I- W 1 Afiorweysf A. E. KEITH.

NON-GROUNDED 0R METALLIC CIRCUIT SYSTEM. APPLICATION F |LED APR. 18, 1901. RENEWED MAR. 29.1919.

1,3213 1 3. Patented Nov. 11, 1919. I 2 SHEETSSHEEI 2.

UNITED STATES PATENT OFFICE.

ALEXANDER E. KEITH. OF HINSDALE. ILLINOIS. ASSIGNOR, BY MESNE ASSIGNMENTS, TO AUTOMATIC ELECTRIC COMPANY, A CORPORATION OF ILLINOIS.

NON-GROUNDED OR METALLIC CIRCUIT SYSTEM.

Specificationof Letters Patent.

Patented Nov. 11, 1919.

Application filed April 18, 1907, Serial No. 369,013. Renewed March 29, 1919. Serial No. 286,077.

To (/71 lllmm. it may con cru lie it known that l. .'\I.I'IX.\.\I)ER E. Knrrit, a citizen of the luited States of America and resident of llinsdale, Dupage county, lllinois. have invented a certain new and use lul Improvement in Non-Grounded or Metallic (ircuit Systems, of which the following is a specification.

My invention relates to telephone systems in general. but more particularly to automatic or semi-automatic telephone exchange systems. and especially to systems in'which electrically-propelled and step-by-stepactu ated switching machines, such as automatic trunk or line selectors. are employed at the exchange or central station, and controlled by the subscribers through the medium of suitable electrical impulse transmitters at the substations. In systems of this general character it has. prior to my invention, been customary to employ ground connections at the substations. and to use these ground connections for controlling the automatic switches at the exchange or central station, both for connecting and releasing purposes. Itv is evident. however. that an exchange having operating grounds at the substations is open to more or less objection. and that for obvious reasons itis better to arrange a telephone system in such manner that no ground circuits are necessary between the exchange and substations for controlling the automatic switches and other appa atus ot' the system. For this reason I provide my improved system with telephone lines having no operating grounds outside of the exchangeor central station. and with subscribers substations at which no grounded switching devices are employed for controlling the automatic switches and other apparatus of the system. In this way the subscribers do not employ the ground or earth as a common return between the substations and the exchange or central station, and are able to control all of the exchange or central station apparatus over line circuits including both sides of the linein series, so that no ground circuits are necessary outside of the exchange or central station. \Vith such arrangement I provide each telephone line with an individual trunking switch, or with an automatic switch for selecting idle lines of any suitable character. and make provision tor operating and releasing these switches over circuits including both sides of the telephone lines, which latter are of the complete metallic circuit type. As herein disclosed, these individual switches for the telephone lines are provided with switch wipers adapted to be raised to the desired level and then rotated in such level to find.

an idle line. which latter may be a trunk line leadmg to any other suitable apparatus.

Thus it. will be seen that I provide an autochange and the substation from which the switching machine is being controlled or operated. As herein disclosed, the automatic switch thus controlled or operated from a non-grounded substation is adapted to be re leased by suitable means at the said substation. or to be released manually by an operator or attendant at the exchange or central station. As previously explained, the lines leading from the said automatic machine can be either trunk lines or telephone lines, or may be lines for some other purpose, depending upon the size and characterot the system. The nature and advantages of my invention will, however, hereinafter more fully appear.

In the accompanying drawings, Figure 1 illustrates diagrammatically the impulsetransmitting means at the leftand the controlled means at the right connected by a line composed of two conductors.

Fig. 2 isa diagrammatic illustration of a highly improved form of subscrihers telephone apparatus comprising the impulsetransmitting means shown at the left of Figit l.

Fig. 3 is a diagrammatic perspective view of aselector switch C, showing the circuits and n'iechanism in detail. Said selector is a modified form of the type of selector disclosed in United States Letters Patent No. 815,321, granted March 18, 1906. to Keith, Erickson & Erickson.

Referring to Fig. 1. the impulse-transmitting means here represented comprises the springs 2 and 3. the spring 2 being connected directly to the line conductor 4. and the spring 3 being connected directly to'the line conductor 5. Said springs '2-'and 3 are. as shown, normally disconnected. The said line conductors l and 5 are shown normally connected through two other springs 6 and 7 which are normally in contact. The spring 6 is directly connected to the conductor 5, while the spring 7 is connected through a high resistance coil 8 to the con: ductor 4; therefore, normally, the conductors 4 and 5 are in a series circuit comprisingthe high resistance coil' 8 and the springs 7 and 6. At the central office the line A, which is composed of the conductors at and 5, terminates in the line relays 9 and 10, one terminal of the relay 9 being connected directly to theconductor 4, and one tern'iinal of the relay 10 being connected directly to the conductor 5. The other terminal of the relay 9, as shown, is connected to the nongrounded terminal of battery B, while the other terminal of the relay 10 is connected to the grounded terminal of the battery B. As shown, the positive terminal of the battery B is connected to ground at G. Fun thermore, the conductors 4 and 5 are, as shown, connected with a switch C, such as a selector or connector of any suitable type. The relay 9, as shown, has under its control the spring 11. while the relay 10 has under its control the spring 12, and between said springs 11 and 12 is situated a grounded spring 13. From the spring 11 is shown a lead 14 that terminates in the switch C, and from the spring 12 is shown another lead 15 that also terminates in the switch C. When the relays 9 and 10 are operated they cause electrical circuits of any suitable character to be set up for operating any proper mechanism comprised in the switch 0. This mechanism can be caused to carry the wipers 1G and 17 into engagementwith any line, whereby, for example, the conductor -l may be extended to the conductor 18 and the conductor 5 to the conductor 19 of the de sired line. At the same time a third wiper 20 may be carried into engagement with a contact 21 for setting up any potential that will guard the seized line, and also into connection with the conductor 22 leading from the contact 21, which may be employed for any circuit-controlling purpose whatever, such as releasing. Therefore, by connecting the conductors 4 and 5 with the-conductors 18 and 19 a circuit may be established with a telephone, for example, for the purpose of carrying on conversation.

I do not, however. limit myself to telephone circuits, as telegraph circuits may be set up in the same manner. The subscribers instrument shown in Fig. 2, which comprises the impulse-transmitting means, may be of any suitable character; but I have elected to disclose my impulse-transmitting means in connection with the particular type of telephone shown in Fig. *2, which comprises many well known features. The receiver 28, switch-hook 24E, transmitter 25,

induction-coil 26, local battery 27 and ringer 28 will be recognized.

Through. the medium of the switch-hook the local circuit comprising the battery 27 and transmitter 25 are controlled at a point between the springs 29 and 30, and by means of the springs 32 and 33 the ringer 28 is bridged across the line when the switch-hook is down. l urthermore. through the n'iedium of the switch-hook the spring 7 is held normally disconnected from thehigh resistance coil 8. and the line conductors 4: and 5 are, therefore, retainednormally disconnected at this point; but when the switch-hook is up the springs 31 and 32 come into contact, the spring 32 leaving the spring 33, whereby the ringer 28 is disconnected from the line, and the conductors t and 5 connected through the high resistance coil 8 and the springs 7 and. 6. he substation is provided with a shaft 34-, that carries a dial (not shown) having indications of a suitable nature, to guide a subscriber in makin a call. On the said shaft there is mounted an impulse wheel provided on its periphery with whatmay be, for convenience and clearness, designated as vertical impulse teeth 36 and a rotary impulse tooth 37, which tooth 37 is separate and distinct from the teeth 36 and is used for operating the springs 6 and 7, while the teeth 36 are used for operating the springs 2 and 3-that is, the springs 6 and T are adapted to be separated, and the springs 2 and 3 are adapted to be pressed into contact. The operation of the substation impulse-transmitter may be more minutely described as follows: order to transn'iita number of impulses the dial is so rotated as to cause the impulse wheel to first rotate in the direction indicated by the arrow, which operation does not materially affect the springs 2, 3, 6 or 7, and, therefore, does not affect the circuits; but when the dial is released a suitable spring returns the dial and impulse wheel in the opposite direction, at which time the vertical impulse teeth 36 engage the spring 2 one at a time, each one pressing the spring 2 onto the spring 3, and thus SllOI't-(J-il'CUitil'lg the line conductors 4 and 5 each time; then, just before the dial comes to a standstill the tooth. 3T withdraws the spring 7 from the spring 6, thus sep arating the line conductors -l and 5, as already indicated. It will be seen that in this way the springs 2 and 3 may be brought into contact a suitable number of times, and the springs 6 and 7 separated once each time that the dial is operated. The effect of this mode of operation may be described as follows: If a call is to be madethe rc ceiver 23 is removed from the switch-hook 24, at which time the springs 31 and 32, controlled by said switch-hook. come into contact and a circuit setup (as indirated in Fig. 1) through the line relays t) and 10, which includes the line conductors l and 5. the. high resistance coil 8, the springs 6 and T and the central battery B. The line relays 9 and 10 are suitably wound, the latter to a comparatively high resistance and the former to a comparatively low resistance. so that when a circuit is established. as stated, the line relay 10 is operativcly energized, while the line relay 9 does not opcratively energize. The circuit over which the current that energizes the line relay 10 flows extends from the non-grounded terminal of battery B to the line relay 9, thence to the line conductor 4, through the high resistance coil 8. springs 31 and 3:2, rotary impulse springs T and (5, line conductor 5 and rotary line relay 1() to the grounded terminal of battery B. \Vhen the line relay 10 energizes, the springs 13 and 12 are then brought into contact and, the conductor 15 is thus placed in connection with the grounded terminal of battery B, and any desired circuit may thus be established through the switch C. After the switchhook is thus permitted to rise and the above relays have operated, then if the dial is operated, as already explained, the springs 2 and 3 are pressed into contact a number of times and the springs 6 and 7 are, after this, separated once. Each time that the springs Z and 3 are pressed into contact the high resistance coil 8 is short-circuited, whereby the current-fl0w through the vertical line relay 9 is increased for operatively energizing said relay. It will be understood, of course, that each time the springs 2 and 3 separate, the current in this circuit again diminishes, and consequently the line relay 9 again resumes its normal condition. Each time that the relay 9 energizes, the springs 11 and 13 are pressed into contact, whereby the conductor 1 1 is connected with the grounded terminal of battery B for the purpose of establishing another circuit that may be traced through the switch C. After the last impulse has been delivered for operating the vertical line relay 9, and after the said relay has returned to normal condition, the springs 6 and 7 are separated for an instant, whereby the line circuit is broken and the rotary line relay 10 is deenergized. This relay. upon regaining its normal condition, permits the springs 13 and 12 to separate, disconnecting the conductor 15-.fro1n the grounded terminal of battery B. It will be understood that thedenergization of the relay 10 is simply momentary, and consequently the springs 12 and 13 are not retained separated very lon As stated, the selector switch C is a mo ified form of the selector of said patent, and comprises the line relays 9 and 10, already described, the switch shaft 38 which carries the line wipers 16 and 17 and the private wiper 20, already mentioned. These. wipers have banks'39 and l0 (well known) in which terminate lines of any suitable character; The conductors 18. 1t) and .22 are shown terminating, the first two in the line. bank 39, and the last one in the private bank 40 at thecontact 21. The. said switch shaft is also equipped with the cam 41 that controls the cam springs 12 and 13, a set of longitudinal teeth 41, a set of circular teeth 45, and a shaft-controlling spring 16 for restoring the shaft. to normal position. The switch is equipped, furthermore, with the vertical magnet t7 by means of which the switch shaft is given its vertical step-by-step motion. There is also a third magnet 48 for giving the shaft its rotary step-by-step motion, and the private magnet 19 that controls the side switch. the latter comprising the side switch wipers 50. 51. 5'2 and 53. In this selector switch C the means by which the switch is restored after a connection has been made comprises the release magnet 54, and the back-release relay 55, which latter, by means of the springs 56 and 57, controls the energizing circuit of the release 7 magnet 54,

A detailed description of how the line relays 9 and 10 may be used to operate the selector switch C shown in Fig. 3 is as follows: \Vhen the subscriber removes his receiver and energizes the rotary line relay 1() by bridging the high resistance coil 8 across the line conductors 4*. and 5, the private magnet 4.9 then energizes each time the springs 12 and 13 are brought into contact and attracts its armature, and remains so energized until the circuit through the relay 10 is subsequently broken. Then, each time that the vertical line relay 9 energizes, as a result of the bringing together of the springs 2 and 3 at the telephone, the vertical magnet 17 is energized each time that the springs 11 and 13 are brought into contact. Each time that the vertical magnet =17 energizes, of course, the pawl controlled by said magnet engages the circular teeth 45 and raises the shaft one step. After the shaft has been raised, then when the springs 6 and? are separated and the rotary line relay 10 is deenergized as a result, as explained, the private magnet 19 deenergizes and allows the side switch to trip from first to second position, at which time the side switch wiper 50 engages the grounded contact point 58, setting up, as a result, an 'energizing circuit through the rotary magnet 48, which magnet then operates to rotate the shaft one step, placing the line wipers 16 and 17 and the private wiper '20 in engagement with the first contact of the'level of their respective banks to which the shaft has been previously raised, which in this case is assumed to be the second level. It the first nine trunks of that level are busy the first nine contacts of the second level of the private bank 40 will be grounded, and as soon as the private wiper 20 engages the first grounded contact an energizing circuit is set up through the private magnet 19, before the cam springs 42 and 43 have time to separate, whereby the private magnet 49 is retained energized and the side switch locked in second position until the wipers are advanced beyond the last busy trunk line. The energizing circuit for said private magnet extends from the grounded contact point to the private wiper 20,'thence through the back-release relay 55, side switch wiper 51, contact point 59, conductor 60, private magnet 49, thence through battery B to ground G. It will be understood that the bac-krelease relay 55 is of comparatively low resistance, much lower in fact than the private magnet 19 in order to permit the private magnet 49 to energize without the relay 55 energizing. It will be found that this combination can be had by making the relay of one-half ohm resist ance and the private magnet 49 of from three-hundred to five-hundred ohms resistance where the battery B is of about fifty volts. As soon as the private wiper 20 passes the last grounded contact point the private magnet 49 deenergizes and permits the side switch to trip to third position, at which time the line conductors 4 and 5 are extended through the side switch wipers 52 and 53, contact points 61 and (32, conductors 63 and 64: to the line wipers 16 and 17, and thence to the trunk conductors 18 and 19. Also, the side switch wiper 51 engages the grounded contact point (35, whereby a guarding potential is established at the private wiper 20 for protecting the seized line. The trunk conductors 18, 19 and 22 may lead to any desired point, such as an operators cord circuit, a subscribers talking set, or a signaling device of any character, from which point the switch C may be released and the established connection destroyed if the release conductor 22 is connected to the non-grounded terminal of battery B. \Vhen the back-release relay is of onehalf ohm resistance there should, of course, be a moderate resistance in series with the conductor 22, so that the current through the said coil 55 will not be excessive. A circuit being established, the current will pass through the resistance a to the conductor 22, thence to the private wiper 20 and through the back-release relay 55 to the grounded terminal 65 and back to battery B. The relay 55 will then attract its armature and press the springs 57 and 56 together, which will then establish an encrgizing circuit through the release magnet 5-l as follows: from ground through the springs 57 and 5G to the release magnet 51, thence through battery B to ground G.

circuit.

The said magnet 54, upon attracting its armature, will move the double dog (36 so as to lock it with the release link (37, thus depriving the shaft 38 of its retaining means and permitting it to return to normal position. It will be evident, however, that such a release circuit is not absolutely necessary in all cases, for there may be certain conditions in which it is not desired that the switch C should be released over a release In that event the switch (1 may be released manually by some attendant who may cause a release by simply pressing the double dog (56 and causing it. to be locked by the release link 67. Such an arrangement might be used in connection with lire alarm circuits and in any other connection where, after a connection is once established, it should not be destroyed until recorded It will be obvious that if it is desired the conductors 1S and 19 may terminate in relays 68 and (if), similar in character to the line relays 9 and 10. and when connection is made with the conductors l6 and 15,) the rclay (35) may be made to energize like thc rclay 10, and the springs Ti) and T1 are brought into contact. whereby a signaling circuit may be established. This signaling circuit may comprise a lamp or a hell or any sig naling means whatever. After the signal has been transmitted or the conversation completed the calling subscriber at the telephone may himself restore the connection by pressing the button 72, whereby the spring 73 is pressed onto the contact point Tl and the line comluctors '-l and 5 are short-circuitcd, the same as it the springs 2 and 3 had been pressed into contact. Of course, the relay (38 will then energize in series with the relay (3!) (the latter being connected to ground and the former to the non-grounded tern'iinal oi the battery 13). whereby the spring 75 will be pressed onto the spring 70, the spring 70 being connected to the nongrounded terminal of the battery 13, instead of to the grounded terminal of said battery B, as is spring 13 at the relays E) and 10. The spring will then have to be connected to the coil (1, and a circuit will be cstablishcd through the back-release relay 55, as already explained, and as a result the release magnet 51 will energize to restore the switch C. It will be understood, of course, that the release button 72 will not be pressed until after the receiver 23 has been restored to the switch-hook.

The circuits may be so arranged that either the operator, as already explained, by pressing the springs at I) in contact, may cause a release, or the subscriber, by energizing the relay 68, may also cause the release.

From the foregoing it will be seen that I provide an improved system in which automatic switches are controlled from nongrounded substations, and releasing purposes. The lines leading from the switch 0 may be thetelephone lines or trunk lines or lines for other purposes, according to the size and character of the system. As explained, I use complete metallic circuits for controlling both the Vertical and the rotary motions of the switch shaft 38, and I also then use a completemetallic circuit for initiating the re lease or restoration of the said switch. The controllin circuits thus include the two sides of t e line in series, and the. ground or earth between the substation and the exchange is not employed for any purpose whatever. In this way I provide an automatic or semi-automatic telephone or other system in which no operating grounds are necessary outside of the exchange or central station. This, of course, is of considerable advantage, as 1t eliminates the objections and difiiculties which usually follow from the use of grounded circuits between the central station and the substations, and which are well known and well understood.

What I claim as my invention.is:-

1. In a telephone system, an automatic switch for selectingtrunks, complete metalthe opera-- lie line circuits for controlling tions of said switch by transmltting a pluboth for connecting.

rality of impulses over two sides, of a line circuit in series, a trunk-release circuit for said switch, and means under the control of a central operator for closing said trunkrelease circuit.

2. In a telephone system,a line, an automatic switch, trunk lines accessible to said switch and leading to an operators position, means for transmitting a plurality of impulses over the two sides of said line in series to cause said switch to select an idle one of said'trunk lines, and means controlled 3. In a telephone system, a line an automatic switch, trunk lines accessible'to said by the operator for releasing said switch.

switch and leading to an operators osition,

talking conductors for said trun lines, means for transmitting a plurality of impulses over' the two sides of said 'line in series to cause said switch to select an idle one of said trunk lines, a release circuit forsaid switch separate from the talking conductors, and means'controlled by the operator for closing said release circuit.

Signed by me at Chicago, Cook county, Illinois, this 12th day of April, 1907.

ALEXANDER E. KEITH.

Witnesses:

EDWARD D. FAnEs, ARTHUR B. SPERRY. 

